1. Field of the Invention
The present invention relates to a semiconductor device and a method of producing the same and, more particularly, to a semiconductor having a plastic package and a method of producing it.
2. Description of the Related Art
FIG. 30 shows a configuration of the semiconductor device having a plastic package according to the prior art. A semiconductor chip 32 is carried on the die-pad 31, and a plurality of inner leads 34 are disposed on the peripheral area of the die-pad 31. As shown in FIG. 31, the inner leads 34 and corresponding electrodes pads 33 are connected by wire-bonding by means of respective metallic fine-wires 35. Each inner lead 34 is integrally connected with a corresponding outer lead 37. The die-pad 31, the semiconductor chip 32, the inner leads 34, and the metallic fine-wires 35 are sealed in a body 36 of the package made of an epoxy resin and the like in a manner such that the outer leads 37 extend to the outside of the body 36. Each outer lead 37 is bent along the shape of the body 36 of the package.
A description of the method of wire-bonding is given below. Commonly, a gold wire having a diameter from 25 to 30 .mu.m is employed as the metallic fine-wire 35. An end portion of the metallic fine-wire 35 being run through a capillary chip (not shown in FIGS. 30 and 31) is heated and melted to form a round ball. A metallic-diffusion bonding between the ball and the electrode pad 33 is executed by applying load, heat, and ultrasonic energy to the ball, and then pressing it onto the electrode pad 33 of the semiconductor chip 32 by means of the capillary chip. Subsequently, the extra amount of the metallic fine-wire 35 is fed out from the capillary chip, and then the metallic fine-wire 35 is pressed onto the inner lead 34, thus enabling metallic-diffusion bonding between each metallic fine-wire 35 and inner lead 34.
The wire bonding is achieved by the above mentioned method; however, the following conditions must be satisfied for accomplishing completely reliable bonding:
1. The electrode pads 33 must be disposed on a peripheral area of the surface of the semiconductor chip 32 to prevent contact between the metallic fine-wire 35 and the edge portion of the semiconductor chip 32. PA1 2. The distance between each electrode pad 33 and the semiconductor chip 32 must be 0.5 mm or more. PA1 3. The clearance between each inner lead 34 and the die-pad must be 0.2 mm or more to insulate them from each other. PA1 4. Each inner lead must have a length of at least 0.2 mm for bonding of the metallic fine-wire 35.
In order to fulfill all of the above requirements, the thickness of the body 36 of the package surrounding the semiconductor chip 32 must be at least 0.5 mm.
In accordance with the contemporary trend of high density integration and advanced functions of an IC device, the size of the semiconductor chip is becoming larger than before, whereas downsizing is required with respect to the package size of a semiconductor device in order to comply with demands for downsizing and miniaturizing of electronic equipment. As described above, it is required of the semiconductor device having the conventional configuration to have a thickness of 0.5 mm or more in a body of the package surrounding the semiconductor chip to ensure the reliability of the device; however, there is a drawback that a large semiconductor chip cannot be accommodated in a downsized package-body.